Groups report early safety data, progress on Ebola vaccines

Vaccine in arm
Vaccine in arm

Sean Warren / iStock

Indications from early human trials of an Ebola vaccine developed by Canadian scientists show no serious adverse reactions so far, according to Swiss researchers, as a research team from the United Kingdom announced the launch of a prime-boost study of another Ebola vaccine developed by the US National Institutes of Health (NIH) and drug maker GSK.

For the Canadian-developed vaccine, some volunteers experienced mild -to-moderate inflammatory reactions, according to a machine translation of a Dec 2 press release in French from University Hospitals of Geneva (HUG) where the trial is under way.

The vaccine, called VSV-EBOV, uses an Ebola virus protein spliced into a vesicular stomatitis virus (VSV). NewLink Genetics, a small pharmaceutical company based in Ames, Iowa, obtained the marketing rights to the vaccine from the Public Health Agency of Canada in 2010, but on Nov 24 announced a deal with Merck designed to tap into the larger company's capacity and expertise to get the vaccine through testing, regulatory approval, and production.

VSV-EBOV is one of two Ebola vaccines that are furthest along in clinical trials. The other, called ChAD3, uses a modified chimpanzee adenovirus and was developed by the US National Institute of Allergy and Infectious Diseases (NIAID) at the NIH and by GSK. Research studies have suggested that the Canadian vaccine would require only one dose, compared with two doses that may be needed for the NIH-GSK vaccine.

So far 34 of 115 people at HUG have been immunized. Participants received an injection containing a lower or higher dose or placebo. All were carefully monitored for an hour and a half after injection, and they were asked to record any symptoms during the week after. They returned to the clinical center for monitoring and sampling on days 1, 2, 3, and 7.

The reactions reported were expected and temporary, lasting a few hours to 2 or 3 days.

The trial continues through early 2015, with 15 more volunteers vaccinated each week, according to the statement. Clinical trials of the VSV-EBOV are also under way in Canada, the United States, Germany, and Gabon, and should start soon in Kenya.

NIH-GSK vaccine trial

In the other vaccine trial development, researchers at the University of Oxford in the United Kingdom today announced the launch of a trial to see if a booster vaccine can increase the immune response to a monovalent version of ChAD3.

The vaccine in the Oxford trials contains genetic material from the Zaire species of Ebola, the strain causing West Africa's outbreak. Initial results from the first human trial of a version of ChAD3 designed to protect the Zaire and Sudan Ebola strains, published last week, showed promising safety and immunogenicity findings.

In a statement today the university said 30 of 60 people who have been vaccinated in ongoing trials of ChAD3were invited to receive a second candidate Ebola vaccine made by Danish pharmaceutical company Bavarian Nordic. The trial is testing the safety of the booster given 3 to 10 weeks after vaccination with ChAD3, and researchers will measure immune responses over 6 months.

The booster vaccine, called multivalent MVA-BN Filo, is designed to protect against the Zaire and Sudan Ebola strains and Marbug virus, another member of the filovirus family, according to a press release today from Bavarian Nordic. The company said recent preclinical studies suggested that an MVA-based booster dose may offer stronger and more durable immune response.

Adrian Hill, MD, PhD, who is leading the trial, said in the statement that the goal of this arm of the trial is to gauge the safety of the two Ebola vaccines used together, as well as the immune response.

"If a single dose of an Ebola vaccine is sufficient, it makes absolute sense to use that. But it also makes sense at this early stage of trials to see if a second booster vaccine can greatly increase the levels of immune responses produced," Hill said in the statement.  He added that there is a lot of uncertainty about the levels of immunity that are needed to protect people against Ebola.

"The more data we have, the more we can make good decisions on what is likely to be safe, what may offer best chance of protection and what is feasible and achievable," he said.

Researchers expect to publish their initial findings by Christmas, according to the statement.

Emory admits potentially exposed health worker

An American health worker who was possibly exposed to the Ebola virus while working in West Africa arrived at Emory University Hospital today for testing and evaluation, a further sign of the ongoing threat to medical responders in the outbreak region.

In an update yesterday, the World Health Organization (WHO) said 622 health workers have been infected with Ebola through Nov 30.

In a statement today, Emory said the patient arrived at 5:45 am by Phoenix Air. It said it couldn't share any other details about the patient, due to privacy rules and the individual's request.

The patient is the seventh American worker to be airlifted from the region, six of whom were health workers. The last one was Martin Salia, MD, a Sierra Leone native and US resident who died from Ebola on Nov 17 at Nebraska Medical Center.

In late September another American health worker was transported to the United States for testing and observation after potential Ebola exposure. Lewis Rubinson, MD, PhD, had suffered a needle stick injury while working for the WHO in Sierra Leone and was evacuated to the NIH Clinical Center in Bethesda, Md., for testing and evaluation.

Though he had some Ebola symptoms such as fever and nausea, his tests were negative for Ebola, and he was released to home quarantine. Rubinson directs the critical care resuscitation unit at the University of Maryland's Shock Trauma Center.

In further health worker developments, another doctor from Sierra Leone has been infected with Ebola, the eleventh from that country struck by the virus so far, the Associated Press (AP) reported yesterday. Dauda Koroma, MD, tested positive for the disease on Dec and is being treated at a military hospital in Freetown, the AP said, citing Brima Kargbo, MD, the country's chief medical officer.

Of the 622 health workers who have been infected with Ebola, 339 of them have died, the WHO said. The total reflects an increase of 30 infections and 6 deaths since the WHO's previous update on Nov 26.

Other developments

  • Doctors without Borders (MSF) yesterday said a US government program to reward pharmaceutical companies for investing in research and development for neglected diseases—which it says will soon include Ebola—will enrich drug companies without assurances that patients, providers, and governments will have access to affordable drugs. In a statement, it said the Food and Drug Administration (FDA) priority review voucher provides a drug maker that registers a qualifying neglected disease medicine in the United States for the first time with a voucher that fast- tracks any other drug in its portfolio. It said companies that receive the vouchers are allowed to sell them to other companies. Judit Rius Sanjuan, US manager and legal policy advisor to the MSF Access Campaign, said in the statement that the group welcomes incentives for accelerating research and development efforts for Ebola and that the US Senate recently made some welcome changes, such as increasing the list of diseases, but is concerned that access to the resulting drugs and vaccines isn't addressed.

  • Officials from the FDA yesterday pushed for randomized, controlled trials for evaluating potential treatments for Ebola in the wake of West Africa's Ebola outbreak. In a commentary in the New England Journal of Medicine, the group wrote that it's understandable why some groups would support "historically controlled" studies that make investigational drugs widely available, and then compare mortality rates of those treated with what would have been expected with past experience with Ebola. The authors are Edward Cox, MD, MPH, Luciana Borio, MD, and Robert Temple, MD. They said the historically controlled trial design could falsely suggest a benefit or fail to detect a modest but meaningful benefit. They also noted that identifying an external group similar enough to compare study outcomes is difficult. The authors also said that historical case-fatality reports would be irrelevant if current patients are receiving better supportive care.

  • The risk of Ebola virus transmission to a pet such as a dog or cat is very low, according to a joint risk assessment today from the European Centre for Disease Prevention and Control (ECDC) and the European Food Safety Authority (EFSA). The agencies said the risk is considered very low because a patient infected with Ebola in Europe is likely to be identified and isolated at an early stage of illness. Though big knowledge gaps remain, the assessment said, so far there is no evidence that dogs can develop and transmit the virus or that cats can be infected.

See also:

Dec 2 University Hospitals of Geneva statement

Dec 4 University of Oxford press release

Dec 4 Bavarian Nordic press release

Dec 4 Emory Healthcare statement

Dec 3 AP story

Dec 3 MSF statement

Dec 3 N Engl J Med commentary

Dec 4 ECDC-EFSA risk assessment on domestic pets and Ebola

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